596 L. H. GODGH. 



University of Basle^ in whose laboratory this paper was 

 prepared, and to Prof. R. Burckhardfc, to whom I am much 

 indebted for the help he rendered me during my studies, and 

 more especially whilst woi'king at this paper. 



I must also express thanks publicly to Dr. Goelde and 

 Dr. Hagmann for having procured me the materials, and to 

 my friend and fellow-student Oscar Huber, for some of the 

 drawings given in this paper. 



Technical Eemakks. 



It was at first very difficult to obtain good cuts through the 

 eggs, because of the presence of the great amount of yolk 

 which they contained. When embedded in paraffin the yolk 

 always crumbled away before the knife of the microtome. 



The following is the method I usually used: — The embryos 

 were brought through successive degrees of alcohol into 

 absolute alcohol. Next they were left in celloidin for some 

 days. They were then taken from the celloidin and put 

 directly into chloroform. This has the double effect of 

 making the celloidin firm, and of rendering the embryos 

 ready to be transferred into paraffin. After having been 

 treated thus, the embryos were cut as ordinary paraffin 

 objects. The cuts Avere attached to the object-glass wntli 

 water; when all the cuts were arranged on the glass, the 

 water was quickly removed with a piece of blotting-paper, 

 whereupon very fluid celloidin was poured over the cuts; 

 they were then allowed to dry, but being still enclosed in 

 paraffin the cuts could not shrink in any way. When quite 

 dry the coating of celloidin became very thin indeed. 



To remove the paraffin I ngain always used chloroform. 

 Afterwards the cuts were treated in the usual manner. In 

 this way I managed to obtain several perfect series, the 

 yolk remaining in its place without being liable to crumble. 



The staining was' always done with eosin and htematoxylin, 

 and invariably after cutting, the outer cuticle of the embryos 

 being impermeable to the reagents used. 



